Re-entry catheter

ABSTRACT

Total occlusions are crossed by passing a guidewire or other penetrating wire from a point proximal to the occlusion into a subintimal space between the intimal layer and adventitial layer of the blood vessel wall. The wire is advanced to a point distal to the occlusion and thereafter deflected back into the blood vessel lumen, typically using a deflecting catheter which is advanced over the guidewire after it has been positioned within the subintimal space. After the guidewire is returned to the blood vessel lumen, the deflecting catheter may be withdrawn and the guidewire is available for introduction of other interventional and diagnostic catheters.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to medical devices, kits,and methods. More particularly, the present invention relates to systemsand procedures for crossing chronic total occlusions in blood vesselswith guidewires and subsequently performing angioplasty, atherectomy,stenting, or other treatments.

[0003] Cardiovascular disease is a leading cause of mortality worldwide.Cardiovascular disease can take many forms, and a variety of specificinterventional and pharmaceutical treatments have been devised over theyears with varying levels of success.

[0004] A particularly troublesome form of cardiovascular disease resultswhen a blood vessel becomes totally occluded with atheroma or plaque,referred to as a chronic total occlusion. Until recently, chronic totalocclusions have usually been treated by performing a bypass procedurewhere an autologous or synthetic blood vessel is anastomoticallyattached to locations on the blood vessel upstream and downstream of theocclusion. While highly effective, such bypass procedures are quitetraumatic to the patient.

[0005] Recently, catheter-based intravascular procedures have beenutilized to treat chronic total occlusions with increasing success.Catheter-based intravascular procedures include angioplasty,atherectomy, stenting, and the like, and are often preferred becausethey are much less traumatic to the patient. Before such catheter-basedtreatments can be performed, however, it is usually necessary to crossthe occlusion with a guidewire to provide access for the interventionalcatheter. In some instances, crossing the occlusion with a guidewire canbe accomplished simply by pushing the guidewire through the occlusion.The guidewire remains in the blood vessel lumen and provides the desiredaccess path. In many cases, however, the guidewire inadvertentlypenetrates into the subintimal space between the intimal layer and theadventitial layer of the blood vessel as it attempts to cross theocclusion. Once in the subintimal space, it is very difficult and inmany cases impossible to direct the guidewire back into the blood vessellumen. In such cases, it will usually be impossible to perform thecatheter-based intervention and other, more traumatic, procedures mayhave to be employed.

[0006] For these reasons, it would be desirable to provide methods,kits, and apparatus which facilitate crossing a chronic total occlusionin a blood vessel with a guidewire. In particular, it would be desirableto provide catheters, guides, or other apparatus which could be usedwith a conventional or specialized guidewire to direct or redirect theguidewire from the subintimal space back into the blood vessel lumenafter the guidewire has entered such space. Such methods and apparatusshould be useful in coronary arteries as well as other blood vessels andshould be capable of being performed with or without imaging from withinor adjacent to the blood vessel. The apparatus for achieving theseobjective should be of simple construction and be capable of being usedin a straight-forward, generally fool-proof manner. At least some ofthese objectives will be met by the invention described hereinafter.

[0007] 2. Description of the Background Art

[0008] Catheters having side guidewire entry ports spaced proximallyfrom their distal tips are described in U.S. Pat. Nos. 5,464,395;5,413,581; 5,190,528; 5,183,470; 4,947,864; and 4,405,314. Catheters andmethods for forming lateral penetrations through tissue to and fromblood vessels past total occlusions are described in U.S. Pat. Nos.5,443,497; 5,429,144; 5,409,019; 5,287,861; WO 97/13463; and WO97/13471.

SUMMARY OF THE INVENTION

[0009] According to the present invention, methods are provided forcrossing total occlusions in blood vessels. While the methods areparticularly beneficial for the treatment of coronary artery disease,they are also useful in the treatment of other arteries and veins, suchas the treatment of peripheral vascular diseases.

[0010] The total occlusions are crossed by first forming a track from alumen in the blood vessel into a subintimal space between an intimallayer and an adventitial layer of the blood vessel. The track is formedso that it extends from a location proximal of the total occlusion to alocation which is distal to the total occlusion. A passage is thenformed from the track back into the blood vessel lumen at the distallocation. In the specific embodiments, the track is formed by advancinga wire through the blood vessel lumen into the subintimal space,typically by advancing the wire until it encounters the total occlusion.By continuing to advance the wire, it will usually pass into thesubintimal space and can be further advanced to the desired distallocation. After the wire is located distally to the total occlusion, itis typically deflected from the track back into the blood vessel lumen.

[0011] In the exemplary methods, the wire is deflected using adeflecting catheter. Typically, the deflecting catheter is advanced overa proximal end of the wire and advanced into the track within thesubintimal space. The wire and the deflecting catheter are thenmanipulated so that the wire is deflected laterally through the intimallayer back into the blood vessel lumen. Such deflecting catheters arealso useful in supporting the wire as it is advanced into and/or throughthe track, i.e. the catheter can enhance the “pushability” of the wirewhen it is advanced forward through any resisting material. Specificdesigns for such deflecting catheters are described in detail below.Alternatively, the wire which is initially positioned within the trackin the subintimal space may be withdrawn through the deflecting catheterand exchanged for a second wire or other device suitable for penetratingthrough the intimal layer back into the blood vessel lumen. It will beappreciated that the wires and/or deflecting and other catheters may befreely exchanged over or through one another in a conventional matterwithout departing from the present invention.

[0012] It will usually be necessary to determine when the wire and/ordeflecting catheter are positioned distal to the total occlusion so thatthe wire may be returned to the blood vessel lumen beyond saidocclusion. Most simply, such position determination can be made byfluoroscopically imaging the blood vessel in a conventional manner.Alternatively or additionally to such fluoroscopic imaging,intravascular imaging, e.g. intravascular ultrasonic imaging (IVUS), anda variety of optical imaging modelities, such as optical coherencetomography (OCT), may be employed. For example, an ultrasonic imagingguidewire may be used to initially access the subintimal space and/ormay be exchanged for the wire which is used to access the subintimalspace. An imaging guidewire present in the subintimal space may readilydetect the presence or absence of occluding material within the bloodvessel lumen. When the transition from occluding material to lack ofoccluding material is detected, it is known that the position of theguidewire has advanced beyond the total occlusion.

[0013] After the passage is formed back from the track into the bloodvessel lumen and a wire is in place across the total occlusion, the wireis available for use as a guidewire in positioning interventional anddiagnostic catheters across the total occlusion. Most commonly,interventional catheters will be positioned across the total occlusionfor treating the occlusion. Exemplary interventional catheters includeangioplasty balloon catheters, rotational atherectomy catheters,directional atherectomy catheters, stent-placement catheters, and thelike.

[0014] In a preferred aspect of the methods of the present invention,the wire deflecting step will comprise deflecting a cannula from thesubintimal space back into the blood vessel lumen and thereafter passingthe wire through a path defined by the cannula, typically by a lumenwithin the cannula. Usually, the cannula will be advanced over the wireafter the wire is disposed within the subintimal space, and thecannula-deflecting step will comprise advancing a resilient (pre-formed)curved end of the cannula from a constraining lumen into the bloodvessel lumen. Alternatively, the wire-deflecting step may compriseadvancing a deflecting catheter over the wire which has been advancedinto the subintimal space. A cannula may then be advanced through alateral opening of the deflecting catheter and penetrated through theintimal layer to define a path for the wire back into the blood vessellumen. Steerable and other actively deployed cannulas may also be used.

[0015] The present invention further provides kits comprising awire-deflecting catheter having a lumen or mechanism capable oflaterally deflecting a wire. The kit will further comprise instructionssetting forth any of the methods described above. optionally, the kitmay further comprise the wire which is used for penetrating thesubintimal space and/or back into the blood vessel lumen. The kit willusually still further comprise a package for containing both the wiredeflecting catheter and the instructions, and optionally the additionalwire(s). Suitable packages include pouches, trays, tubes, boxes, and thelike. The instructions may be printed on a separate package insert ormay be printed in part or in whole on the packaging itself. Usually, thecomponents of the kit within the package will be sterilized byconventional procedures.

[0016] Apparatus according to the present invention comprisewire-deflection systems. Exemplary wire-deflection systems usuallycomprise the wire-deflecting catheter which includes a catheter body anda deflecting cannula. The catheter body will have a proximal end, adistal end, and at least one lumen extending through at least a distalportion thereof. The lumen will have a distal opening and a lateralopening. The cannula also has a proximal end, a distal end, and at leastone lumen extending through a distal portion thereof. The distal portionof the cannula will have a pre-formed, resilient curve. The cannula willbe slidably disposed within the lumen of the catheter body to assume (a)a straightened configuration when the cannula is proximally retractedwithin the catheter body lumen and (b) a curved configuration when thecannula is extended laterally through the lateral opening of thecatheter body. In this way, the cannula can be selectively deflectedthrough the intimal layer of the blood vessel according to the preferredmethods described above. The system may further comprise a wireconfigured to pass through the cannula lumen. The wire may be aconventional guidewire, but will more typically be a wire having asharpened distal tip intended particularly for penetrating the intimallayer of the blood vessel wall. Optionally, the wire may furthercomprise an imaging means such as an ultrasonic imaging means. Thecatheter body will typically have a fluoroscopically visible marker nearits distal end. The marker will be configured to permit visualdetermination of the rotational orientation of the distal end of thecatheter body when viewed in a two-dimensional fluoroscopic image. Thecatheter body will usually be reinforced to enhance torsional rigidity,and may further comprise a distal nose cone wherein the distal andlateral openings are defined within the nose cone. The distal end of thecannula will usually be pre-formed in a smooth curve which may extendover an arc in the range from 15° to 135°, usually from 45° to 90°. Thepre-formed curve may have a radius in the range from 0.5 mm to 15 mm,usually from 2 mm to 10 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a schematic illustration of a coronary artery showingthe intimal layer, the medial layer, and the adventitial layer.

[0018]FIG. 2 is a schematic illustrations of a total occlusion withinthe coronary artery of FIG. 1, shown in full section.

[0019] FIGS. 3A-3D illustrate the method of the present invention forcrossing a total occlusion with a wire using a deflecting catheter.

[0020] FIGS. 3BB illustrates an alternate guidewire advancement step forthe method of FIGS. 3A-3D.

[0021]FIG. 4 illustrates a first embodiment of the distal end of adeflecting catheter suitable for use in the methods of the presentinvention.

[0022]FIG. 5 illustrates a second embodiment of the distal end of adeflecting catheter useful in the methods of the present invention.

[0023]FIG. 6 illustrates a third embodiment of the distal end of adeflecting catheter useful in the methods of the present invention.

[0024]FIG. 7 illustrates a presently preferred embodiment for thewire-deflecting catheter and system of the present invention.

[0025]FIGS. 8 and 9 are detailed, cross-sectional views of the distalend of the catheter of FIG. 7, illustrating an internal cannula in aretracted and advanced configuration, respectively.

[0026]FIG. 10 is a schematic illustration of a proximal hub of thecatheter of FIG. 7.

[0027]FIGS. 11A and 11B illustrate a configuration for rotationallykeying the proximal end of the catheter of FIGS. 7-10.

[0028]FIG. 12 illustrates a configuration for rotationally keying thedistal end of the catheter of FIGS. 7-10.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

[0029] Referring to FIG. 1, a normal (non-diseased) artery A comprisesan arterial wall having a number of layers. The innermost layer isreferred to herein as the intimal layer I which includes theendothelium, the subendothelial layer, and the internal elastic lamina.A medial layer M is concentrically outward from the intimal layer, andan adventitial layer AL is the outermost layer. Beyond the adventitiallayer AL lies the extravascular tissue. As used hereinafter, the regionbetween the intimal layer I and the adventitial layer AL, generallyincluding the medial layer M, will be referred to as the subintimalspace. It is the subintimal space through which the wires, deflectingcatheters, and other catheter of the present invention will pass whencrossing a total occlusion.

[0030] Referring now to FIG. 2, a total occlusion TO within the artery Ais illustrated. Total occlusion TO may comprise atheroma, plaque,thrombus, and/or other occluding materials normally associated withcardiovascular disease. By “total” occlusion, it is meant that theoccluding material occludes substantially the entire lumen L of theartery or other blood vessel so that blood flow through the vessel issubstantially stopped. The present invention will usually be used withpatients where the totally occluded artery is not immediately lifethreatening since the tissue distal to the occlusion will receiveoxygenated blood from collateral arteries. Usually, however, the bloodsupply will be insufficient and it will be desirable to treat theocclusion by an intravascular intervention, such as angioplasty,atherectomy, stenting, or the like, to restore blood flow through theaffected vessel.

[0031] The method of the present invention will be described withreference to FIGS. 3A-3D. These figures represent an upper portion ofthe artery of FIG. 2. As seen in FIG. 3A, a wire 10 is advanced throughthe lumen of the artery until it encounters the total occlusion TO. Atthat time, it is possible that the wire 10 will advance through theocclusion without deflecting into the blood vessel wall. Should thatoccur, subsequent repositioning of the guidewire according to themethods of the present invention may not be necessary. More usually,however, the wire 10 will advance into the subintimal space within themedial layer M, as shown in FIG. 3A. The intimal layer I and adventitiallayer AL together define a “tissue plane” through which the wire willnaturally pass as the wire is pushed distally from its proximal end. Thewire 10 will continue to advance until its tip passes beyond the distalend of the total occlusion TO, as shown in FIG. 3B. The tip couldaxially advance well beyond the total occlusion until advancement isceased.

[0032]FIG. 3B shows the guidewire 10 advancing without support. In someinstances, however, the guidewire 10 may encounter significantresistance as it enters and/or passes through the space between theintimal layer I and adventitial layer AL. If resistance is encountered,the deflection, catheter 20 may be used to support and enhance the“pushability” of the guidewire 10 by advancing the catheter to alocation just proximal of the distal tip of the guidewire, as shown inFIG. 3B. The guidewire 10 and catheter 20 may then be advancedsequentially, e.g. advancing the guidewire a short distance followed byadvancing the catheter, and so on.

[0033] According to the present invention, however, once the wire 10 hasits distal tip positioned beyond the total occlusion TO, deflectingcatheter 20 may be advanced over the wire 10, by coaxial introductionover the proximal end of the wire, until it approaches the totalocclusion, also as shown in FIG. 3B. The deflecting catheter 20 is thenfurther advanced over the wire 10 until its distal tip also extendsbeyond the total occlusion TO, as illustrated in FIG. 3C. The deflectingcatheter 20 will include some mechanism for laterally deflecting thewire 10 so that it may pass back in a radially inward direction throughthe intimal layer I back into the blood vessel lumen L. The deflectionmechanism may take a variety of forms as described below. As shown inFIG. 3C, a lateral port 22 is provided. The wire 10 may be retracted sothat its distal tip lies proximally of the port 22 and then advanceddistally so that the wire passes laterally outwardly through the portand back into the blood vessel lumen, as shown in FIG. 3D.

[0034] In order to optimize performance of this method, it is usuallydesirable to assure that the distal tip of the wire 10 and thedeflecting port 22 (or other deflecting mechanism) of the deflectingcatheter 20 are properly positioned beyond the total occlusion TOwithout being advanced excessively beyond the end of the totalocclusion. Typically, it will be desirable to position the deflectingmechanism at from 0 cm to 2 cm beyond the distal end of the totalocclusion TO, preferably from 0 cm to 0.5 cm. As discussed above, suchpositioning can in some instances be performed using conventionalfluoroscopic imaging. For example, in some instances it may besufficient to provide suitable radiopaque markers on the wire and on thedeflecting mechanism of the deflecting catheter 20 permitting visualpositioning of the tip via fluoroscopy. Often, however, it will bedesirable to provide ultrasonic or other imaging at or near the totalocclusion. In one approach, wire 10 may be provided with ultrasonicimaging so that the presence and absence of the occluding material maybe detected as the wire is advanced passed the total occlusion TO.Alternatively, the deflecting catheter 20 may be provided with suchultrasonic imaging, e.g. in the form of a phased array located near thedistal tip (not shown). Ultrasonic imaging guidewires are described inthe patent literature. See, e.g. U.S. Pat. No. 5,095,911, the fulldisclosure of which is incorporated herein by reference. As yet anotheralternative, an imaging guidewire may be advanced to the region of thetotal occlusion TO in a direction opposite to that of the wire 10 andcatheter 20. In this way, the imaging guidewire need not advance throughthe total occlusion, but could still detect advancement of the catheterand/or guidewire, particularly if ultrasonically opaque components wereprovided on either or both of the catheter and wire. In yet anotheralternative, an ultrasonic imaging catheter or guidewire could bepositioned in a vein adjacent to the arterial occlusion site, allowingimaging of the entire occluded region while the guidewire is advancedthere through. Other imaging modalities, such as optical coherencetomography (OCT) (see U.S. Pat. Nos. 5,321,501; 5,459,570; 5,383,467;and 5,439,000) fluorescence imaging (see U.S. Pat. Nos. 4,718,417; and5,106,387) and Raman spectroscopy (WO 92/18008), may also be employed.

[0035] A second desirable feature of the method of the present inventionwill be rotational positioning of the deflecting catheter 20. It will beappreciated that the direction of deflection is usually selective, andtherefore it will be desirable to aim the deflecting mechanism from thesubintimal space back toward the arterial or other blood vessel lumen L.If the catheter 22 is provided with ultrasonic imaging, such imaging canbe used for rotationally positioning the distal tip of the catheter. Thecatheter will be rotationally rigid so that rotation of its proximal endmay position the distal end. By then detecting the presence of the bloodvessel lumen, the deflecting port 22 or other deflecting mechanism canbe properly positioned. In an alternative embodiment, as illustratedbelow in connection with the exemplary catheter, a rotationally specificfluoroscopic marker may be provided on the catheter 20. The marker willbe such that by observing the two-dimensional image of the marker byfluoroscopic imaging, the rotational direction of the catheter tip canbe determined.

[0036] Referring now to FIGS. 4-6, exemplary deflecting mechanisms forthe deflecting catheters of the present invention will be described. InFIG. 4, the distal end of the catheter 30 has a distal port 32, alateral port 34, and a passive deflecting mechanism 36. The catheter 30may be advanced over the proximal end of a wire so that the wire passesover the deflecting mechanism 36 and back into the main lumen of thecatheter 30. The catheter 30 may then be advanced over the wire untilthe distal tip enters the subintimal space and approaches the distal endof the wire. By retracting the distal end of the wire within the lumenof catheter 30 so that its distal tip is proximal to the deflectingmechanism 36, subsequent distal advancement of the wire will engage theproximal surface of the deflecting mechanism and cause the wire to bedeflected laterally through lateral port 34.

[0037] A first active deflecting mechanism is illustrated in FIG. 5.There, catheter 40 has a distal port 42 and a lateral port 44. Ratherthan a passive deflecting mechanism, catheter 40 includes an axiallytranslatable cannula 46 having a resilient, pre-formed distal tip whichmay be advanced through port 44, as shown in broken line. The cannula 46has a lumen which-provides a guide path for the wire.

[0038] Catheter 50 illustrated in FIG. 6 is similar to catheter 40 inFIG. 5, except that no lateral port is provided. Instead, a cannula 52having a pre-formed distal end may be advanced and retracted out of adistal port 54 of the catheter 50 so that its distal end can assume alaterally deflected shape, as shown in broken line. It will beappreciated that these three embodiments are intended to be exemplaryonly. A wide variety of other passive and active deflecting mechanismscould be provided on deflecting catheters for use in the methods of thepresent invention.

[0039] Referring now to FIGS. 7-10, a presently preferred exemplarydeflecting catheter 100 constructed in accordance with the principles ofthe present invention will be described. The deflecting catheter 100comprises a catheter body 102 having a distal end 104 and a proximal end106. Catheter body 102 includes a single lumen 108 (FIGS. 8 and 9), anda deflecting housing 110 secured to the distal end 104 thereof. Anactuator hub 112 is secured to the proximal end 106 of catheter body102, and an axially translatable cannula is disposed within lumen 108.The cannula 114 has a sharpened tip 116, typically formed from a metal,hard plastic, composite, or the like, optically being radiopaque.Alternatively or additionally, it may be desirable to provide at leastone separate radiopaque marker or the cannula at or near its distal endto facilitate visualization under fluoroscopic imaging. A distal length118 of the cannula 114 is pre-formed in a curved shaped, as best seen inFIGS. 7 and 9. A rotationally specific radiopaque marker 120 is mountednear the distal end of catheter body 102. As illustrated, the marker hasa generally U-shaped configuration so that the rotational position ofthe distal end of the catheter body 102 will be apparent when the markeris observed in a two-dimensional fluoroscopic image.

[0040] As with catheter 40 in FIG. 5, the purpose of catheter 100 is tolaterally deflect the distal tip of the cannula 114 through a lateralopening 122 in the deflector housing 110. The deflector housing 110 alsoincludes a distal port 124 to permit introduction of the catheter 100over the proximal end of a guidewire GW, as illustrated in FIG. 8 inbroken line. The guidewire GW will pass through the distal port 124 andinto the distal end of the cannula 114 and travel through a lumen ofcannula 114 all the way to the proximal end of the catheter 100. Thedistal length 118 of cannula 114 will be straightened and deflected byaxially retracting and advancing the cannula between the configurationshown in FIG. 8 and FIG. 9, respectively.

[0041] Referring now to FIG. 10, the actuator hub 112 comprises a pairof coaxial, telescoping tubes 130 and 132. The outer telescoping tube132 is connected to a proximal end of cannula 114, typically by anadhesive 134. A proximal fitting 136 is further attached to the proximalend of tube 132 so that the assembly of the cannula 114, tube 132, andfitting 136 will move together as a unit through the hemostatic fitting140 at the proximal end of the hub 112. Hub 112 further includes arotational fitting 142 which permits the catheter body 102 to be rotatedrelative to the hub body. The cannula 114 and catheter body 102 will berotationally coupled or “keyed” together to limit or prevent relativerotation, typically by keying within the hub and/or near the distal end,so that rotation of the catheter body causes a like rotation of thecannula as the catheter is rotationally positioned within a bloodvessel. A side branch 148 is provided on hub 112 to permit perfusionand/or infusion through the lumen 108 of catheter 102.

[0042] Keying at the proximal end of the catheter 100 can be achieved ina variety of ways. For example, the telescoping tubes 130 and 132 can beprovided with asymmetric, mating peripheral geometries, such as ovalcross-sections (FIG. 11A) or triangular cross-sections (FIG. 11B).Keying at the distal end can also be achieved in a number of ways, suchas providing the catheter body 102 with an asymmetric lumen 108 and thecannula 114 with a mating cross-section, e.g. a D-shaped cross-sectionas illustrated in FIG. 12. The ability to limit relative rotation of thecannula 114 within the catheter body 102 is advantageous since itassures that curved distal length 118 is properly oriented (usuallydirected radially outwardly) when the tip 116 emerges through theopening 122.

[0043] In use, catheter 100 will be advanced over guidewire GW while thecannula 114 is retracted, as shown in FIG. 8. Once the catheter isproperly positioned, cannula 114 may be distally advanced, as shown inFIG. 9. Distal advancement is achieved by forwardly advancing the sleeve132 in hub 136 relative to the remainder of the hub 112 so that thecannulas move forwardly within the lumen 108 of catheter body 102. Priorto advancing the cannula, the port 122 will be properly positioned sothat it is directed toward the blood vessel lumen by rotating catheterbody 102, typically using the rotational hub 142. Conveniently, thephysician will observe the marker 120 so that the lateral port 122 willbe directed in the proper radially inward direction. After the cannulahas been advanced into the blood vessel, the guidewire GW may then beadvanced into the lumen, the cannula 114 withdrawn proximally, and theentire catheter assembly then withdrawn from over the guidewire, leavingthe guidewire in place for introduction of other interventional and/ordiagnostic catheters.

[0044] While the above is a complete description of the preferredembodiments of the invention, various alternatives, modifications, andequivalents may be used. Therefore, the above description should not betaken as limiting the scope of the invention which is defined by theappended claims.

What is claimed is:
 1. A method for crossing a total occlusion in ablood vessel, said method comprising: forming a track from a lumen inthe blood vessel into a space between an intimal layer and anadventitial layer of the blood vessel, said track extending fromproximal of the total occlusion to past the total occlusion; andselectively forming a passage from the track back into the blood vessellumen at a location distal to the total occlusion.
 2. A method forcrossing a total occlusion, said method comprising: forming a track froma lumen in the blood vessel into a space between an intimal layer and anadventitial layer of the blood vessel, said track extending fromproximal of the total occlusion to past the total occlusion, anddeflecting a wire from the track back into the blood vessel at alocation distal to the total occlusion.
 3. A method for crossing a totalocclusion in a blood vessel, said method comprising: advancing a wirethrough a lumen of the blood vessel into a space between an intimallayer and an adventitial layer of the blood vessel to create a track insaid space past the total occlusion; and selectively forming a passagefrom the track back into the blood vessel lumen at a location distal tothe total occlusion.
 4. A method for crossing a total occlusion in ablood vessel, said method comprising: advancing a wire through a lumenof the blood vessel into a space between an intimal layer and anadventitial layer of the blood vessel; and deflecting a wire from thesubintimal space back into the blood vessel lumen a location distal tothe total occlusion.
 5. A method as in any of claims 1 to 4, wherein theblood vessel is an artery.
 6. A method as in claim 5, wherein the arteryis a coronary artery.
 7. A method as in any of claims 1 to 4, furthercomprising performing an interventional or diagnostic procedure over awire disposed in the subintimal space.
 8. A method as in either claim 2or claim 4, further comprising advancing an interventional or diagnosticcatheter over the deflected wire from proximal to the occlusion, throughthe subintimal space, back into the blood vessel lumen.
 9. A method asin any of claims 1 to 4, further comprising imaging the occlusion andblood vessel lumen to identify the location distal to the totalocclusion.
 10. A method as in claim 9, wherein the imaging stepcomprising imaging from within the subintimal space or blood vessel. 11.A method as in claim 9, wherein the imaging step comprises imaging froma position external to the subintimal space and the blood vessel.
 12. Amethod as in claim 9, wherein the blood vessel is a coronary artery andthe imaging step comprises imaging from a position in a vein adjacent tothe coronary artery.
 13. A method as in claim 4, wherein a single wireis both advanced into the subintimal space and deflected back into theblood vessel lumen.
 14. A method as in claim 4, further comprisingexchanging a first wire which is advanced into the subintimal space fora second wire which is deflected back into the blood vessel lumen.
 15. Amethod as in claim 4, wherein the wire deflecting step comprises:deflecting a cannula from the subintimal space into the blood vessellumen; and passing the wire through a path defined by the cannula.
 16. Amethod as in claim 15, wherein the wire deflecting step furthercomprises advancing the cannula over the wire after said wire isdisposed within the subintimal space and before the cannula isdeflected.
 17. A method as in claim 16, wherein the cannula-deflectingstep comprises advancing a resilient curved end of the cannula from aconstraining lumen into the blood vessel lumen.
 18. A method as in claim4, wherein the wire deflecting step comprises advancing a deflectingcatheter over the wire which has been advanced into the subintimalspace.
 19. A method as in claim 18, further comprising passing a cannulathorough a lateral opening of the deflecting catheter and penetratingthe cannula through the intimal layer, wherein the wire is thereafteradvanced through a lumen of the cannula.
 20. A method as in claim 19,wherein the wire deflecting step comprises: retracting the wire into thecannula lumen before the cannula is passed through the lateral openingof the catheter; and advancing the wire through the cannula after saidcannula has been passed through the lateral opening of the catheter. 21.A method as in claim 19, wherein the deflecting step comprises:withdrawing the wire from the cannula; and introducing a second catheterinto the cannula and through said cannula after said cannula has beenpassed through the lateral opening of the catheter.
 22. A method as ineither claim 20 or claim 21, wherein the catheter and cannula arewithdrawn from over the wire after said wire has deflected into theblood vessel lumen.
 23. An improved method for advancing a guidewirethorough a subintimal space between an intimal layer and an adventitiallayer and past a total, occlusion in a blood vessel, wherein theimprovement comprises selectively deploying the guidewire through apassage from the subintimal space back into the blood vessel lumen. 24.A kit comprising: a wire; a wire deflector having a lumen which deflectsa wire laterally; and instructions setting forth use of the wiredeflector according to any of claims 1 to
 4. 25. A kit as in claim 24,wherein the wire, the wire deflector, and the instructions are packagedtogether in a single container.
 26. A kit as in claim 24, furthercomprising a wire.
 27. A wire deflection system comprising: a catheterbody having a proximal end, a distal end, and at least one lumenextending through at least a distal portion thereof, wherein said lumenhas a distal opening and a lateral opening; and a cannula having aproximal end, a distal end, and at least one lumen extending through adistal portion thereof, wherein said distal portion has a pre-formedresilient curve and wherein said distal portion of the cannula isslidably disposed in the lumen of the catheter body to assume (a) astraightened configuration with said cannula lumen axially alignedwithin the distal opening of the catheter body when the cannula isproximally retracted within the catheter body and (b) a curvedconfiguration with the cannula extending laterally through the lateralopening of the catheter body when the cannula is distally advancedwithin the catheter body.
 28. A system as in claim 27, furthercomprising a wire configured to pass through the cannula lumen.
 29. Asystem as in claim 27, wherein the wire has a sharpened distal tip. 30.A system as in claim 27, wherein the wire comprises means for imagingtissue surrounding the wire.
 31. A system as in claim 27, wherein thecannula comprises a self-penetrating distal end.
 32. A system as inclaim 31, wherein the self-penetrating distal end comprises a sharpeneddistal tip.
 33. A system as in claim 27, wherein the cannula comprises aradiopaque marker near its distal end.
 34. A system as in claim 27,wherein the catheter body has a fluoroscopically visible marker near itsdistal end wherein said marker permits visual determination of therotational orientation of the distal end of the catheter body.
 35. Asystem as in claim 27, wherein the catheter body is reinforced toenhance its torsional rigidity.
 36. A system as in claim 27, furthercomprising a distal nose cone attached to the distal end of the catheterbody, wherein said nose cone defines the distal and lateral openings.37. A system as in claim 27, wherein the pre-formed curve in the distalend of the cannula extends over an arc in the range from 15° to 135°.38. A system as in either claim 27 or 37, wherein the pre-formed curvehas a radius in the range from 1 mm to 20 mm.
 39. A system as in claim27, further comprising a hub rotationally secured to a proximal end ofthe catheter body.